Abstract: In this paper we discuss the Mather problem for stationary Lagrangians, thatis Lagrangians $L:\Rr^n\times \Rr^n\times \Omega\to \Rr$, where $\Omega$ is acompact metric space on which $\Rr^n$ acts through an action which leaves $L$invariant. This setting allow us to generalize the standard Mather problem forquasi-periodic and almost-periodic Lagrangians. Our main result is theexistence of stationary Mather measures invariant under the Euler-Lagrange flowwhich are supported in a graph. We also obtain several estimates for viscositysolutions of Hamilton-Jacobi equations for the discounted cost infinite horizonproblem.